1. Field of the Invention
The present invention relates to a capacitive element and, particularly, an integrated capacitive element. In particular, the present invention relates to an integrated thin film capacitive element which comprises a substrate such as semiconductor substrate having at least one capacitor structure formed by using a thin film fabrication process. The present invention also relates to a method for producing the capacitive element of the present invention and an electronic device using the capacitive element of the present invention.
2. Description of the Related Art
Recently, the increased processing speeds of LSIs have led to the development of decoupling as a strategy for preventing diffusion of high-frequency noise, and an improvement of the high-frequency tracking performance of the decoupling capacitors used is now desired.
To achieve an improved high-frequency tracking performance of decoupling capacitors, the decoupling capacitors must have characteristics such as high capacitance and low impedance connections in distributed circuits, and it is known that this requirement can be achieved by forming thin film capacitors on a semiconductor substrate by a thin film fabrication process. The thin film capacitors are also called thin film capacitive elements or devices.
Because the thin film capacitors are miniature, have large capacities and are excellently suited for microprocessing, they can be connected with a circuit board through a bump connection with narrow pitches between terminals, thereby reducing mutual inductance and making possible effective low-inductance connections with LSIs. Generally, the thin film capacitors comprise a substrate having applied thereon a capacitor structure consisting of a dielectric layer sandwiched between a lower electrode layer and an upper electrode layer. One example of the thin film capacitors having such a structure is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2000-49311. In the capacitive device disclosed in JPP'311, a lower electrode, a capacitive insulating layer consisting of insulating metal oxide which is a ferroelectric or high dielectric material, an upper electrode and a protective insulating layer are formed in this order on a substrate. In this capacitive device, the protective insulating layer has contact holes to connect the lower electrode to a wiring circuit thereof and to connect the upper electrode to a wiring circuit thereof, and the contact holes have an opening area of not more than 5 μm2. The capacitive device can solve the problem that a metal oxide used in the formation of the dielectric layer can be reduced during production of the capacitive device, thereby causing deterioration in electrical characteristics of the resulting device.
With regard to the metal oxide constituting the dielectric layer of the thin film capacitive elements, thin film ABO3 perovskite type dielectric materials such as barium strontium titanate are currently being investigated as voltage tunable capacitive elements for applications in microwave and RF devices and as charge storage devices for decoupling capacitor and DRAM applications. For these applications, a high voltage tunability of capacitance ΔC(V) and/or high capacitance density is required. ΔC(V) can be defined as ΔC(V)=100×(Cmax−Cmin)/Cmin where Cmax is the maximum in capacitance density and Cmin the minimum capacitance density over the operating voltage.